Conventionally, an electrophotographic printer being an image forming apparatus has a built-in light source unit, called a print head, which selectively emits light to a photoreceptor, thereby forming latent images. (See Patent Documents 1 to 3.)
In the print head of Patent Document 1, a head substrate (450; glass substrate) provided with a group of light emitting elements (410), a light shielding member (440) in which light guiding holes (4410) are formed, and a micro lens array (430) are fixed to a case (420) in a state of being stacked in this order. More specifically, the head substrate is arranged between the case and a back cover (470), and the back cover is pressed to and fixed to the case with a retainer (460). The light shielding member and the micro lens array are fitted into and fixed to an opening part of the case. In this configuration, light of the light emitting elements passes through the light guiding holes, and forms, with the micro lens array, images on a photoreceptor.
The print head of Patent Document 2 employs the same configuration as the print head of Patent Document 1. Besides, in Patent Document 2, there is disclosed an embodiment in which (i) a head substrate (450) and a light shielding member (440) and (ii) the light shielding member and a micro lens array (4301) are each glued with an adhesive (436).
In the print head of Patent Document 3, LED elements (30) are fixed to a holder (34) via a wiring substrate (33), and a lens array unit (1) in which lens plates (11) including micro lenses (12) are fixed to a light shielding member (13) is also fixed to the holder.